1. Field of the Invention
The invention relates to a power conversion apparatus and particularly relates to a power conversion apparatus that utilizes a voltage conversion characteristic to achieve a digital to analog conversion signal feedback mechanism.
2. Description of Related Art
Power conversion apparatuses are used mainly for converting high-voltage and lowly-stable AC input power, supplied by the power company, to low-voltage and highly-stable DC output power that is suitable for various electronic devices. Therefore, power conversion apparatuses are widely used in electronic devices, such as computers, office automation equipment, industrial control equipment, and communication equipment.
The conventional power conversion apparatus is usually provided with a power factor correction (PFC) circuit in the front-end stage for providing a constant DC input voltage (up to 380V for example) to a DC-to-DC conversion circuit in the back-end stage. No matter the power conversion apparatus is in the state of light load or heavy load, the PFC circuit provides constant high voltage (380V) to the DC-to-DC conversion circuit in the back-end stage. Thus, under the principle of constant power, power loss of the power conversion apparatus during light load increases (compared with heavy load), which lowers the overall conversion efficiency of power conversion apparatus.
In view of the above, a power conversion apparatus with a feedback control mechanism has been proposed, which allows the controller that controls the front-end stage PFC circuit to adjust the output voltage of the PFC circuit according to the operation status of the load, so as to improve the conversion efficiency. In the power conversion configuration with the feedback control mechanism, the controller that controls the back-end stage DC-to-DC conversion circuit needs to feed information associated with the operation status of the load back to the front-end stage controller.
If the back-end stage controller and the front-end stage controller are a digital circuit and an analog circuit respectively, a (chip type) digital-to-analog converter (DAC) is required to be disposed between the two controllers for performing digital to analog conversion, so as to feed the information associated with the operation status of the load from the back-end stage controller back to the front-end stage controller. However, due to limitation of the conversion characteristic of the general (chip type) digital-to-analog converter, the digital signal outputted by the back-end stage controller cannot be converted to a proportional analog signal through the digital-to-analog conversion. For this reason, an additional digital to analog converter needs to be disposed, which raises the design costs of the power conversion apparatus.